Diagnostic and Treatment Approach for Leukocytosis and Thrombocytosis

Initial Diagnostic Steps

The National Comprehensive Cancer Network recommends establishing whether the patient has a primary myeloproliferative neoplasm or a reactive process to determine the treatment strategy 1, 2
Peripheral blood fluorescence in situ hybridization (FISH) using dual probes for BCR and ABL genes is mandatory to confirm or exclude chronic myeloid leukemia (CML) 1, 2

The National Comprehensive Cancer Network suggests that tyrosine kinase inhibitors should be started immediately once the Philadelphia chromosome or BCR-ABL1 fusion gene is detected 3, 1, 2
Imatinib is the first-line treatment for chronic phase CML, according to the National Comprehensive Cancer Network 1, 2, 4
BCR-ABL transcript levels must be measured every 3 months during treatment, as recommended by the National Comprehensive Cancer Network 1, 2
Bone marrow cytogenetics should be performed at 6 and 12 months from therapy initiation, according to the National Comprehensive Cancer Network 1, 2

Hydroxyurea is the first-line drug of choice for cytoreductive therapy in both ET and CML when needed, as recommended by the National Comprehensive Cancer Network and the Journal of Clinical Oncology 1, 2, 5, 4
Dosing for symptomatic thrombocytosis: Hydroxyurea 2-4 g per day to restore platelet counts to <400×10⁹/L, according to the Journal of Clinical Oncology 5, 4
Dosing for symptomatic leukocytosis: Hydroxyurea 50-60 mg/kg per day until WBC <10-20×10⁹/L, as recommended by Blood 6, 7

For symptomatic thrombocytosis, evaluate for microvascular symptoms and consider age, cardiovascular risk factors, and degree of thrombocytosis when deciding treatment, according to the Journal of Clinical Oncology and the National Comprehensive Cancer Network 5, 1, 2
Aspirin is contraindicated in young patients with CML due to risk of acquired von Willebrand syndrome and bleeding complications, as recommended by Leukemia 3

Complete blood counts should be done weekly until stable, then every 2-4 weeks, as recommended by the National Comprehensive Cancer Network 1, 2
BCR-ABL transcript levels should be measured every 3 months if CML, according to the National Comprehensive Cancer Network and Praxis Medical Insights 1, 2, 4
Bone marrow cytogenetics should be performed at 6 and 12 months if CML, as recommended by the National Comprehensive Cancer Network 1, 2